Staff Writer Science Daily
Tomorrow’s fuel-cell vehicles may be powered by enzymes that consume cellulose from woodchips or grass and exhale hydrogen.
Researchers at Virginia Tech, Oak Ridge National Laboratory (ORNL), and the University of Georgia have produced hydrogen gas pure enough to power a fuel cell by mixing 14 enzymes, one coenzyme, cellulosic materials from nonfood sources, and water heated to about 90 degrees (32 degrees Celsius).
The group announced three advances from their “one pot” process: 1) a novel combination of enzymes, 2) an increased hydrogen generation rate — to as fast as natural hydrogen fermentation, and 3) a chemical energy output greater than the chemical energy stored in sugars – the highest hydrogen yield reported from cellulosic materials. “In addition to converting the chemical energy from the sugar, the process also converts the low-temperature thermal energy into high-quality hydrogen energy – like Prometheus stealing fire,” said Percival Zhang, assistant professor of biological systems engineering in the College of Agriculture and Life Sciences at Virginia Tech.
“It is exciting because using cellulose instead of starch expands the renewable resource for producing hydrogen to include biomass,” said Jonathan Mielenz, leader of the Bioconversion Science and Technology Group at ORNL.
The researchers used cellulosic materials isolated from wood chips, but crop waste or switchgrass could also be used. “If a small fraction – 2 or 3 percent – of yearly biomass production were used for sugar-to-hydrogen fuel cells for transportation, we could reach transportation fuel independence,” Zhang said. (He added that the 3 percent figure is for global transportation needs. The U.S. would actually need to convert about 10 percent of biomass – which would be 1.3 billion tons of usable biomass).
The research is supported by the Air Force Office of Scientific Research; Zhang’s DuPont Young Professor Award, and the U.S. Department of Energy.
[Submitted by hempistry]
Tomorrow our vehicles may derive power by enzymes. These enzymes may originate from the cellulose of woodchips or grass and instead of emitting poisonous gases they will exhale hydrogen. We know that when hydrogen is burned, the only emission it makes is water vapor, so a key benefit of hydrogen fuel is that when burned, carbon dioxide (CO2) is not produced. Clearly, hydrogen is less of a pollutant in the air because it omits little tail pipe pollution. Hydrogen also has the potential to run a fuel-cell engine with better effectiveness over an internal combustion engine.
A team of scientists from Virginia Tech, Oak Ridge National Laboratory, and the University of Georgia says it has successfully generated hydrogen gas. Normally these kinds of fuels are derived from starch. Jonathan Mielenz, who is the leader of the Bioconversion Science and Technology Group at ORNL, says, “It is exciting because using cellulose instead of starch expands the renewable resource for producing hydrogen to include biomass.”
This hydrogen gas is clean enough to power a fuel cell by combining 14 enzymes, one coenzyme, cellulosic materials from non-eatable sources, and water heated to about 90 degrees Fahrenheit (32 C). The researchers utilized cellulosic materials which is isolated from wood chips. But researches also claim that crop waste or switchgrass could also be used for this purpose. These research outcomes are being published in ChemSusChem. The research is supported by the Air Force Office of Scientific Research; Zhang’s DuPont Young Professor Award, and the U.S. Department of Energy.
Percival Zhang who is assistant professor of biological systems engineering in the College of Agriculture and Life Sciences at Virginia Tech, states, “In addition to converting the chemical energy from the sugar, the process also converts the low-temperature thermal energy into high-quality hydrogen energy – like Prometheus stealing fire.” This group declares the benefits of their “one pot” process. The first advantage is they are using a unique combination of enzymes. The second advantage is that hydrogen generation rate is as fast as natural hydrogen fermentation. The third advantage is the chemical energy output is greater than the chemical energy stored in sugars. The maximum hydrogen yield is produced from the cellulosic materials.
Percival Zhang said that if we can utilize a small fraction (two or three percent) of annual biomass production (at global level) for sugar-to-hydrogen fuel cells for transportation, it can lead us to transformational fuel independence. For U.S.A. the figure varies a bit. If U.S. wants to get rid of fossil fuels from transport they actually need to convert about 10 percent of biomass – which would be 1.3 billion tons of usable biomass.
[Submitted by kabukisensei]
Staff Writer Science Daily
President Barack Obama’s pursuit of energy independence promises to accelerate research and development for alternative energy sources — solar, wind and geothermal power, biofuels, hydrogen and biomass, to name a few.
For the hydrogen economy, one of the roadblocks to success is the hydrogen itself. Hydrogen needs to be purified before it can be used as fuel for fuel cells, but current methods are not very clean or efficient.
Northwestern University chemist Mercouri G. Kanatzidis, together with postdoctoral research associate Gerasimos S. Armatas, has developed a class of new porous materials, structured like honeycomb, that is very effective at separating hydrogen from complex gas mixtures. The materials exhibit the best selectivity in separating hydrogen from carbon dioxide and methane, to the best of the researchers’ knowledge.
The results, which offer a new way to separate gases not available before, will be published online Feb. 15 by the journal Nature Materials. The materials are a new family of germanium-rich chalcogenides.
“A more selective process means fewer cycles to produce pure hydrogen, increasing efficiency,” said Kanatzidis, Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences and the paper’s senior author. “Our materials could be used very effectively as membranes for gas separation. We have demonstrated their superior performance.”
Current methods of producing hydrogen first yield hydrogen combined with carbon dioxide or hydrogen combined with carbon dioxide and methane. The technology currently used for the next step — removing the hydrogen from such mixtures — separates the gas molecules based on their size, which is difficult to do.
Kanatzidis and Armatas offer a better solution. Their new materials do not rely on size for separation but instead on polarization — the interaction of the gas molecules with the walls of the material as the molecules move through the membrane. This is the basis of the new separation method.
Tests of one form of the family of materials — this one composed of the heavy elements germanium, lead and tellurium — showed it to be approximately four times more selective at separating hydrogen from carbon dioxide than conventional methods, which are made of lighter elements, such as silicon, oxygen and carbon.
“We are taking advantage of what we call ‘soft’ atoms, which form the membrane’s walls,” said Kanatzidis. “These soft-wall atoms like to interact with other soft molecules passing by, slowing them down as they pass through the membrane. Hydrogen, the smallest element, is a ‘hard’ molecule. It zips right through while softer molecules, like carbon dioxide and methane take more time.”
Kanatzidis and Armatas tested their membrane on a complex mixture of four gases. Hydrogen passed through first, followed in order by carbon monoxide, methane and carbon dioxide. As the smallest and hardest molecule, hydrogen interacted the least with the membrane, and carbon dioxide, as the softest molecule of the four, interacted the most.
Another advantage is that the process takes place at what Kanatzidis calls a “convenient temperature range” — between zero degrees Celsius and room temperature.
Small-molecule diffusion through porous materials is a nanoscopic phenomenon, say the researchers. All the pores in the hexagonal honeycomb structure are ordered and parallel, with each hole approximately two to three nanometers wide. The gas molecules are all at least half a nanometer wide.
[Submitted by hempistry]